I recently signed up for a new gym closer to where I live. Together with the signup they were offering structuring a workout schedule with a personal trainer, which I gladly took. After talking about my goals for training and any old injuries, I was told that their general policy with overall workouts is one set and as many reps as possible though at least 10-12 reps, and increasing the weight next session once 12 reps is not tough anymore.
I have to say I was quite unsure about this regime, so I asked the trainer about if they had any reason for recommending this regime and was told that the advice is based on shorter but intensive sessions and is a company policy that is recommended nationally (it's a large company that have gyms overall in the country).
I wonder if there is any physiological reason behind this regime being superior to the usual/conventional 3 set with 12-15 reps? Have you been recommended this regime at some point? If you have followed a similar regime, how does it compare to more conventional regimes? I should note that my goals for workout is recovering from weakness that some old injuries have left as well as my sedentary life style causes, as well as generally getting in better shape.